The ophthalmic artery is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges. Occlusion of the OA or its branches can produce sight-threatening conditions.
Structure
The OA emerges from the internal carotid artery usually just after the latter emerges from the cavernous sinus although in some cases, the OA branches just before the internal carotid exits the cavernous sinus. The OA arises from the internal carotid along the medial side of the anterior clinoid process and runs anteriorly passing through the optic canal with and inferolaterally to the optic nerve. The ophthalmic artery can also pass superiorly to the optic nerve in a minority of cases. In the posterior third of the cone of the orbit, the ophthalmic artery turns sharply and medially to run along the medial wall of the orbit.
The central retinal artery is the first, and one of the smaller branches of the OA and runs in the dura mater inferior to the optic nerve. About 12.5mm posterior to the globe, the central retinal artery turns superiorly and penetrates the optic nerve, continuing along the center of the optic nerve, entering the eye to supply the inner retinal layers.
The OA then turns medially, giving off 1 to 5 posterior ciliary arteries that subsequently branch into the long and short posterior ciliary arteries which perforate the sclera posteriorly in the vicinity of the optic nerve and macula to supply the posterior uveal tract. In the past, anatomists made little distinction between the posterior ciliary arteries and the short and long posterior ciliary arteries often using the terms synonymously. However, recent work by Hayreh has shown that there is both an anatomic and clinically useful distinction. The PCAs arise directly from the OA and are end arteries which is to say no PCA or any of its branches anastomose with any other artery. Consequently, sudden occlusion of any PCA will produce an infarct in the region of the choroid supplied by that particular PCA. Occlusion of a short or long PCA will produce a smaller choroidal infarct, within the larger area supplied by the specific parent PCA.
Muscular branches
The OA continues medially the superior and inferior muscular branches arise either from the OA directly or a single trunk from the OA subsequently divides into superior and inferior branches to supply the extraocular muscles.
The supraorbital artery branches from the OA as it passes over the optic nerve. The supraorbital artery passes anteriorly along the medial border of the superior rectus and levator palpebrae and through the supraorbital foramen to supply muscles and skin of the forehead.
Because of the obvious importance of the ocular globe, branches of the ophthalmic artery often are subdivided into two groups: those that supply the eyeball and those that supply non-ocular orbital structures.
Orbital group
The orbital group, distributing vessels to the orbit and surrounding parts, includes:
Severe occlusion of the ophthalmic artery causes ocular ischemic syndrome. As with central retinal artery occlusions, ophthalmic artery occlusions may result from systemic cardiovascular diseases; however, a cherry-red spot is typically absent and the vision is usually worse. Amaurosis fugax is a temporary loss of vision that occurs in two conditions which cause a temporary reduction in ophthalmic artery pressure: orthostatic hypotension and positive acceleration. Even complete occlusion of the ophthalmic artery may possibly leave the eye without symptoms, probably because of circulatory anastomoses
